1. Field of the Invention
The present invention relates generally to semiconductor fabrication equipment and more specifically to wafer manufacturing, post chemical-mechanical planarization cleaning and particle monitor wafer reclaiming.
2. Description of the Prior Art
Semiconductor processing depends on clean wafers and therefore a clean environment within which to process the wafers. Two methods are conventionally used to obtain clean wafers. A first method includes preventing particulate contamination from occurring, such as doing the wafer processing in a class one hundred cleanroom or a class ten cleanroom. A second method cleans wafers that are dirty, typically with a rinser-dryer. No amount of particulate contamination prevention will keep all wafers clean because some process steps actually generate particulates. Therefore, cleaning of contaminated wafers is almost always necessary.
Double-sided scrubbers, e.g., the OnTrak Systems, Inc. (Milpitas, Calif.) Systems DSS-200 and DSS-150, are directed at applications that require a thorough cleaning of both sides of a wafer. Such systems are being used in semiconductor fabrication (Fab) lines around the world for processes as diverse as bare silicon cleaning by silicon material suppliers to post chemical-mechanical planarization (CMP) for inter-metal dielectric planarization cleaning.
The demand for ever flatter inter-metal dielectrics has increased as semiconductor device geometries continue to shrink. CMP produces a more planar dielectric layer between metal layers by using a silica slurry for a chemical part of the process. If the slurry is not thereafter completely removed, or if it is allowed to dry, so many defects will occur in the individual circuit dice that the whole wafer may have to be scrapped, thus lowering yields and raising unit manufacturing costs.
A conventional double-sided scrubber system has two brush stations that allow for a more thorough cleaning of wafers. A spin station is used to rinse and dry both sides of a wafer without contacting the wafer surfaces. A robot is included that grips cleaned wafers on the edges and places each wafer on a blade that lowers into a wafer cassette. The cassette is positioned on its back to allow a laminar air flow through the cassette. The brushes are constantly flushed with deionized water to inhibit particle buildup. An indexer accepts a cassette of wafers from a previous operation, such as polishing, and will transmit a wafer from the cassette to the cleaning, rinsing and drying stations when appropriate.